Control apparatus responsive to traffic density



Feb.16,1960

Filed Feb. 13, 1956 w. M. JEFFERS 2,925,583

CONTROL APPARATUS RESPONSIVE TO TRAFFIC DENSITY 3 Sheets-Sheet l f \Er iooooboo .F ET 2 67 6B 69 7o INVENTOR.

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Feb. 1 6, 1960 w. M. JEFFERS 2,925,583

CONTROL APPARATUS RESPONSIVE TO TRAFFIC DENSITY Filed Feb. 13, 1956 sSheets-Sheet 3 flE- IN VEN TOR.

BY Miter M. UE/fers United States Patent "CONTROL APPARATUS RESPONSIVETO TRAFFIC DENSITY Walter M. Jelfers, Syracuse, N.Y., assignor toCronse- Hinds Company, Syracuse, N.Y., a corporation of New YorkApplication February 13, 1956, Serial No. 564,949

8 Claims. (Cl. 340-37) This invention has to do with vehicular trafiicsignaling systems and relates more particularly to that type of .systemwherein the signal control apparatus is varied in :timers forcontrolling the display of the trafiic signals .at the variousintersections of the system, the timers being operated by variable speedmotors, the speed of which is determined by the voltage impressed. uponacircuit interconnecting all of the timers. v

The invention has as an object an arrangement inr corporated in such asystem which functions to maintain the voltage on the interconnectingcircuit inproportion to the density of traffic moving throughthe'signalized area.

The invention consists in the novel features and in the combinations andconstructions hereinafter set forth and claimed.

In describing this invention, reference is had to the accompanyingdrawings in which like characters fdesignate corresponding parts in allthe views.

In the drawings Figure 1 illustrates a series of highway intersectionsin a schematic diagram showing the arrangement of the apparatus embodiedin the system.

Figure 2 is a schematic diagram of the master timer and a secondarytimer.

Figure 3 is a schematic. wiring diagram showing a portion of the circuitarrangement of the apparatus for varying the voltage on the cyclecontrol circuit. 7

' Eigure 4, when placed to the right of Figure 3, completes the circuitof the voltage control apparatus;

Referring to Figure 2 of the drawings, indicates the ,motor drivendialof the master controller, this dial being 1 provided with a pin orlobe 2 1 for 'engaging'thc movable contact 22 to move the same out ofengagement with the fixed contact 23 once during each revolution of thedial 20. The dial 20 is rotated by a variable speed motor having adriving coil 24 and a brake coil 25. I

- Each secondary controller of the system has a contact dial 26 providedwith a pin 27 for moving the movable contact 29 into engagement with thefixed contact 32. The dial 26 is also driven by a similar variable speedmotor having a driving coil 34 and a brake coil 36. The

with the master controller once during each revolution of the dial 20.

The hot side 38 of the power line feeding the driving coil 24 isconnected, through wire 39, to the movable contact 22. Inresynchronizing systems of the general type herein disclosed,thecontacts 22, 23, are normally engaged as shown, and the contact 23isconnected through wire 40 to contact 29 which is normally out ofengagement 'withcontact 32. .The contact 32 is connected 2,925,583Patented Feb. 16, 1966 to one side of a relay coil 50, the opposite sideof the coil being connected to a common return conductor 51.

The brake coil 36 normally has voltage applied to it from a wire 53which also applies this voltage to the braking coil- 25 of the mastertimer. The opposite sides of the brake coil 25 and the driving coil 24are connected to the common return 54. Wire 53 is connected to a fixedContact 55 normally engaged by a movable contact 56 connected to thebrake coil 36 through wire 57. The opposite side of the coil 36 isconnected to the common return 51 through wire 58, movable contact 59,fixed contact 69. The voltage thus impressed on the coil 36 deter--mines the braking effect of the coil and accordingly, the

speed at which the dial 26 rotates.

If a secondary timer is out of step with the master, the contacts 29,32, will be closed while the contacts 22, 23, are closed and coil 50will be energized, moving the contact 56 into engagement with a fixedcontact 61 which is connected to the hot. side 38 of the supply. Thistrans fer applies line voltage to the braking coil 36 causing the dial26 to stop and it will dwell until it is released by the opening ofcontacts 22, 23, at the master timer. The

f circuit includes a limiting resistor 62 to reduce the current in thebrake coil 36 so that the dial will not run backwards. The speed controlwire 53 is also connected to a fixed contact 63 which, when relay 50 isenergizedfis engaged by a movable contact 64 connected through a.resistor 65 to the common return wire 51. The purpose of this contactarrangement is to substitute the load of the resistor 65 in place of thecoil 36 so that the removal of the brake coil from the control circuitwill not vary the voltage in that circuit. Also contact 59 is moved intoengagement with contact 66 to shift wire 58 from wire 51 to thelocalcommon 54.

If the secondary timer is in step with the master, the contacts 22, 23,are opened at the same instant contacts 29, 32, are closed, so thatthere is no dwell of the secondary timer. An arrangement of this generaltype is disclosed in Patent No. 1,929,378 to Carl H. Bissell, October 3,1933. a

This invention has to do particularly with the arrangement for varyingthe voltage in the conductor 53 in pro- I wire 73 which extends to thecommon return54.

In like manner, detector 68 is connected through wire 74 to coil 75 ofan associated relay, and detector 69 is connected to coil 76 of anassociated relay, and detector 73 is connected to coil 77 of itsassociated relay. There may be any number of these detectors 67-70employed to take a fair sampling of the traffic moving in the signalized area. Each of the relays 71, 75, 76, 77, has a movable contact78 normally engaged with a fixed contact 79 which is connected throughwire 80, potentiometer 81, wire 82, variable resistor 83, resistor 84,to the plus side of a full wave rectifier 86, 87, supplied by atransformer 88 connected by wires 89, 96, to the feed circuit 39, 54.The movable contact is connected through limiting resistor 92 to avariable condenser 93, the opposite side of which is connected throughwires 94, 95, to a con denser 96.

When the relays 7'1, 75, 76, 77, are deenergized and their contacts 78are in engagement with the contacts 79, the condensers 93 are. chargedthrough the adjustable potentiometer 81. When relay 71 is closed by itsdetector 67, contact 78 is moved'into engagement with contact 100. Thecharge on the condenser 93 is thus transferred through rwires ltl l,102, movable contacts -103, .104,..of.manually.operable switches 105,106, wire 107-, to the. condenser 96.

w The condensers 93 are of relatively small capacity. The condenser '96is of larger capacity and accumulates the charges transferred from thecondensers 93 by actuation of the associated, detector relays 71, 75,76, 77', and this charge is transferred to the grid 110 of tube -.111..The output of tube 111 iscompared with the .voltageon conductor 53which is supplied from a variable. transformer 115, seevFigure 4, andthe resultant of .the. voltage of the tube output and wire 53 is fed to:a..serv o amplifier 116 for the control of a motor 117. The tube 111 issupplied with plate power through the ,transformer 118 and rectifiers119, 120, the output of V @which isfiIteredTbycondenser 121. Thearrangement -.is such..that .if the grid 110 is at zero potential, high=.plate current flows givingva potential drop across resistor -12 lfthegrid 110 is madehighly negative, plate current:..stops and there is'nopotential across resistor 124. aThesgrid-is normally biased so thatthere is no plate scurrent. .Actuations of the detectors 67- 7% decrease-Ihis.bias, allowing plate current. to flow and, as the '.charge on thecondenser 9 6 is increased by successive r.-detector ;actuations, thepotential across the resistor 12 4 51's, increased and accordingly, thevoltage in conductor .12 is.increased. eczBias potential is supplied bythe transformer 126 and '.rectifier,.1 27 and is filtered by thecondenser 128. The .positive.- output is connected through wires 129,130, .-..tot the cathode 131 of tube 111. The negative output connects,to the grid through conductor 134, resistor .135, .wire 136, resistor137. The resistor 137 is provided to limit or prevent excessive gridcurrent when sit has. positive bias.

..z-tive with.respect to the side connected to wire 95. 7 Each 7actuation of a detector transfers a pulse of charging The resistor 138is employed to' agive a definite maximum resistance. from the bottom oftermines the voltage on the wire 53. Also, as previously prect relationto traflic density, the pointer 153 of trans-' former 'must bere-positioned accordingly. This is stated, the pointer 153 is moved byreversible motor 117 through the action of the servo amplifier 116which, in turn, operates according to the function of the voltage ofconductors and 53. The conductor 125 forms a.

portion of a loop circuit starting from the common return wire 5 throughwire 1%, wire 129, the left portion of resistor 124, wire 125, pointer158, wire 159, resistor 160, theleft'portion of resistor 161, wire162,pointer 163, wire 164, resistors 165, 170, 17 1, voltage limiter 172,wire 173, to the common side 54. Two major potentials are injected intothis 'circuitone is that across the resistor 124 broughtabout bydetector actuation. The other is across resistor 165 proportional to thevoltage in conductor 53. The circuit is arranged so that these twopotentials oppose each other. If they are equal, no current flowsthrough the loop. This condition prevails only when the voltage ofconductor 53 is equal to the flow of traflic in the signalized'area.

If the voltage inconductor 53 does nothave the corefiected bylthereversible motor 117 under the' control of the servo amplifier 116. Theamplifier input is taken from the balancing loop or bridge circuitacrossthe coil 201 being connected to the common return 54. This transformerfurnishes voltage to a circuit 204, 205, including a rectifying tube206. This circuit includes a filter'arrangement including the condensers207 and 'resistors 208, 209. With this arrangement, a D.C. voltage is.supplied to the loop circuit through the conductors 204, 205, and thisvoltage is in direct proportion to the ,voltage on the conductor 53. aThe arrangementis' such that the voltage in the circuit 204, 205,opposes the voltage" introduced in the loop circuit by plate currentfrom tube 111 flowing through resistor 124. If these voltages are equal,no current flows through' the loop. The volt- 1 age in the loop circuit,modified by'the voltage in the acuriient, and resistor 141 smooths outthese pulses so that the potentialacross the condenser 140 changes;:;gradually.w The condenser 96 and theresistor 14-1 thus ;,ser.ve; t ofilter out the pulsationsbefore' they can reach t the condenser 140.'The resistor 'notonly couples .;.the grid to the cathode butalso servesas a discharge element for condenser and, by the same token,

v:{condenser 96.. This resistor is continuously removing the charge fromthese condensers. Actuations of the Qdetectors charge the condensers,and resistor 135 is c ontinuously discharging them. The voltage on thecon- ,densers can not rise indefinitely, but will stop when the rat,eofcharge and discharge are equal. Accordingly,

.. the potential across the condenser 140 is therefore proportional totraflic density.

? 1 ..;Eachfof the detector relays 7l, 7s, 76, 77, when ..-energized,acts to increase the charge on the condenser .140. The operation of therelays can be independent or simultaneous since each relay circuit iscomplete in 'itself. .Continuous closure of one relay will not neu-.tralize the others because, it simply holds the small ca- ..pacitor 93.across the condensers 96, 140, producing an effect of no importance. VV

As previously. stated,.the' voltage in conductor 53 is producedby' thevariable transformer 115. .The winding 150..-ofr. the transformer is.connected to the hot'feed 39 =th'rough .wire 151'and to l the return 5l,by wire 152. The movable pointer 153 is connected to wire 53. The

circuit 204, 205, appears across the limiter 172 which consists. ofrectifiers 210, 211, thecharacteristic of which is such that they willnotpass'current ofeny appreciable value unless there is a potential ofone volt or more inf the" circuit. Above this value, they pass currentthat increases rapidly with rise in potential. The resistor absorbs theexcess potential that is "blocked from the amplifier circuit by thelimiter 172. The resistor 171 is employed only to, reduce thesensitivity of the limiter 172. i i

.. The'rnotor 117 could be operated by a polarized'relay with its coilconnected in the bridge or loopcircuit," or

could be controlled by a magnetic amplifierof the proper design.However, when an A.C. servo amplifier is'emv rter to change the DC. toAC. This'rectifier combi- V ployed, as in this case, direct current.output acrossthe limiter 172 will not effect operation of the amplifier.The DC. must be converted to A.C., and rectifiers 220, 221, 223 and 224are used in abridge arrangement as'a connation is fed with about sixvolts AC; from the secondary of a transformer 225, through wires 226,227, and in- 1' cluding a resistor 228. The current from the transformerflows downwardly simultaneously through the two-rectiher arms duringhalfof the cycle. The current is blocked during the other half of thecycle. The rectifiers are matched so that there is no potential betweenthe left and right junctions of the arms connected to the wires 230,

231, when the rectifienbri'clge is balanced. However, if there is a DC.potential fed through the-wires 230,231,

* from the loop circuit, the balance will be disturbed and analternating component will be superimposed upon the i DQ, potential.The. wires 230'; 231, "are connected to also supplied with A.C. powerfrom supply 39, 54, through wires 236,237.

It w'illibe apparent that the polarity of this component will bedependent upon the direction of the bridge unbalance. 'In other words,the polarity in the wires 230, 231, which depends upon the direction ofunbalance in the potential between the loop circuit depending on theoutput of tube 111 by detector actuation, and the potential in thecircuit 204, 205, which is proportional to the potential in wire 53.

The result of this unbalance is the rectifier bridge 220- 224 is a flowof alternating current through the coupling capacity 236 to theamplifier 116. Any frequency components higher than sixty cycles areattenuated by filter condenser 237. Accordingly, there is an AC. inputto the amplifier 116 when the rectifier bridge is unbalanced I and theinstant polarity of the A.C. current with respect to the instantpolarity in the A.C. supply circuit 236, 237, i is dependent upon thedirection of bridge unbalance. This AC. is amplified by the servoamplifier in a conventional manner and applied to the servo motor 117through wire 240.. This current drives the motor in one direction or the=other, causing the movable slider 153 of the auto transi former torotate in such a direction as to rebalance the bridge. This results in asystem of density control wherein the speedof the master and secondarytimer dials 20, 26, operate continuously at a speed comparable totrafiic (density. p 4

It is desirable to provide for certain adjustments in the apparatus tomore elfectively handle traflic condittions existing in a particularinstallation. For example, "it is desirable that the system shouldalways operate on ithe shortest cycle that traffic in the areacontrolled by the system can follow. This gives the maximum speed ofprogression. As tratfic density increases, the cycle period of thetrafiic signal increases, assuming that the vehicles ':are impeded bythe density and can not reach a fast pro.- :gression of speed. Highdensity at low speed should give :a longer cycle to the signals than thesame density at high :speed and this arrangement handles traffic mostefficiently.

It is therefore desirable to provide adjustments so that the trafiiccycle will be controlled in part by the speed of the :moving traffic. Itis also desirable not to have the cycle period shifting or changing fora short or momentary increase in the density of traffic. It is alsodesirable to prov ide iior operation of the system at certain times on afixed Ehasis rather than according to the density of trafiic. My

system provides for such adjustments.

, When the slider of the potentiometer 81 is positioned .at the top ofthe resistor, the condensers 93 charge only 5 :to the grid biaspotential that is across the condenser 123 and resistor 138. Thecapacity of the condensers 93 is low enough so that the quantity ofcharge transferred for actuation is low. If the slider is positioned atthe bottom of the resistor 81, the condensers 93 will charge to a valueequal to the grid bias plus the potential across the resistor :81. Thisgives a high transfer per actuation. "tentiometer 81 therefore may beconsidered as a master weighting control for all detectors and thedetectors can be weighted individually by adjusting the condensers 93.The circuit between the contacts 100 and wire 101 include 'apotentiometer 250 which serves to limit the dischargeof the condensers93 to a safe value and which can be :adjusted so that the completecharge is transferred from.

The po- ;the condensers 93 only for the slowest moving cars.

The potentiometer 161 is employed to adjust the mini- :mum cycle. It isused for injecting an adjustable voltageinto the bridge loop circuit. Afixed potential across the potentiometer 161 is supplied by atransformer 252, rec 'Jtifier 253, 254, and a filter condenser 255. Whenthe :slider of the potentiometer 161 is at the left end of theresistance, as shown in Figure 4, the operation of the bridge circuit isas previously described. If the slider is :moved toward the right, apotential is inserted and polariized to add to that developed in theresistor 124. In this 6 event, even though there is no traffic the servoamplifier receives a voltage and raises the potential on wire 53 'uhtilthe voltage acrossthe resistor 124 equals that inserted or added by 161.This determines the minimum cycle that will be given; v

Provision is made for cancelling out temporarily any cycle increasecompleted by actuation of the detectors. This is accomplished laypressing switch 106. removes the grid of tube 111 from the condensers96, 140, and connects it to the negative bias supply through wire 260.

The maximum cycle period obtained is adjustable by the potentiometer 124for automatic operation. If the slider of this potentiometer is set tothe left end of the resistance, no current is delivered to the loopcircuit and actuation does not increase the cycle. If the slider is setto the extreme right of the resistance, it delivers enough potential towire 125 to give the system maximum cycle. This happens when the gridbias becomes zero. Push button switch 105 when pressed disconnects thegrid of tube 111 from the condensers 96, 140, and it connects the gridto the cathode through wire 261 simulating maximum density. Thepotentiometer 124 can then be adjusted for the maximum cycle byobserving the change in the voltage on conductor 53. In the manipulationof the switches .105, 106, the detector relay contacts 100 aredisconnected from the condensers 96, 140, and the resistor 135. isdisconnected from the condensers. i

For operating the system on fixed cycles, the two gang switcharrangement 158, 163 can be rotated to any one of five positions. Whenswitch 158 is moved out of engagement with the contact of wire 125, theresistor 124 is removed from the bridge circuit. The switch 163 connectsany one of the five potentiometers 269, 270, 271, 272-, 273, to the wire164. This injects an adjustable potential which must be balanced by thepotential at resister 165 and the voltage on Wire 53 automaticallyassunaes the necessary value. The potentiometer 269 may :he set to givea cyclefor example, of fifty seconds; the

potentiometer 27 0 to give a cycle for sixty seconds, and so on.Accordingly, rotation of this gang switch provides any offlzpiuralityofidesired pre-set cycles.

During automatic operatiomit may be desirable to adjust for acertainunregistered density that must be exceeded before any cycleincreaseoccurs. This is accomplished by overbiasing the tube 111. The input tothe bias rectifier 127 comes from the voltage divider 275 connectedacross the secondary of the transformer 126. The resistor 276 has such avalue that when the slider of 275 is at the left end of the resistance,the bias is just enough to stop the flow of plate current. As the slideris moved to the right, the bias is more than enough to stop platecurrent. Then there must be a certain trafiic density before the biaswill be reduced below the cut-oft value of the tube 111, ailowing platecurrent to flow and change the cycle. When this adjustment is made toincrease the unregistered density, it is at the same time desirable toincrease the master Weighting of traflic in order that the master trafdcdensity will give the maximum cycle. To avoid adjustment of thepotentiometer 81, the potentiometer $3 is coupled mechanically to theslider of potentiometer 275, whereby when the slider 275 is moved to theright, the slider of 83 moves upwardly increasing the voltage across 81.This automatically gives the required 7 increase in weighting.

What I claim is:

1. Trafiic signal control apparatus responsive to traffic densitycomprising a master controller, a plurality of variable speed secondarycontrollers operable through repeated cycles for the control of tratficsignals, all of said controllers being connected .to a control circuit,a power supply for said control circuit including a voltage controlmeans adjustable to increase and decrease the voltage on said controlcircuit, each of said controllers having means for operating thecontroller through said "a -speed d epende t ppon --the voltage 'on saidlo q cuin'apl iralityof vehicle-actuated detectors disposedlto'befactuated" by traffic rnovirigunder the connot or saidsignals,"mean'soperable in'respons'e to actuationof said detectors tocontinuously adjust said voltage control irneans to maintain thevoltageon said control circuit ijin proportion'to'the'irequency of saiddetector actuation.

{2.1'lrafiic'control apparatus responsivetotrai'rlc density comprising'aplurality of variable speed controllers operablev through repeatedcycles for the control of traflic signals, all'jofsaid controllers beingconnected to a control circuit, means for energizing said controlcircuit, each bfsaidcontrqllers. having n eans for operating the' con-"troller through said' cycles ata speeddependent upon the .voltage onsaid control circuit, a condenser, a plurality V 'of'vehi'cle 'actuateddetectors disposed to be actuated by i'traiiifimoving under' the controlof said signals, means fior'c'onstantly discharging said condenser,means operable upon each actuationot each detector to increase the"charge on fsa'id condensen and means operable to conitinuou'slyadjust-the voltage on said control circuit in proportiomto the voltageacross said condenser.

l'fTraffic control apparatus responsive to traiiic den- ;sity comprisinga; plurality of variable speed controllers operable throughrepeatedcyclesfor the control of trafiic signals,all of said controllersbeing connected to a control circuit, means for energizing said controlcircuit, each at said'controllers having means for operating'thecontroller through said cycles at a speed dependent upon Tthe'volta'geon said cotnrol circuit, a condenser, a plurality 'ofvehicle actuateddetectors disposed to be actuated by name moving under the control ofsaid signals, means for constantly dischargingsaid condenser, meansoperable upon each" actu'ationof each detector to increase the"chargeion said condenser, an electron amplifying tube 'liavirig'itsinputconnected across said condenser, a voltage control means jconnectedto the output of said tube and T'being operable to continuously-adjustthe voltage on said controlcircuit in proportion to the voltage of theoutput of said tube.

4. Traffic control apparatus responsive to traffic density 'cornprisinga plurality of variable speed controllers operable through repeatedcycles for the control of traffic sig- "nalsgall of said cotnrollersbeing connected to a control circuitpmeans for energizing said controlcircuit, eachof said controllers having means for operating the 1'controller through said cycles at'a speed dependent upon "the voltagecn"said controlcircuit, a condenser, a pin- -rali ty of vehicle actuateddetectors'disposed to be actuated j bytrafiic rnoving under the controlof said signals, means for constantly-discharging said condenser, meansoperable upofe'ach'actuationbt each detector to increase the 1e-'onsaictcohde ranelectron-amp fying.t hehev' ing its input circuitconnected across saidlcgndensena power supply' for said icontrjolcircuit includ ng '.a1 ;adjustable auto .transfiormer,,.a reversibleniotor operatively connected to said transformer for adjusting the same,to increase aridfdec'reaseIthejvoltage in said control circuit, a servoamplifierfor controlling said motor, a bridge pircuit including,theoutput of .said tube connected to said amplifier, and a feedhackcircuit-from said control circuit to said bridge circuit.

'5. Apparatus as defined inclaim 4 vwherein the charge on saidcondenseris increasedbyeacn detector actuation inversely to the speed ofthe vehicle actuating the detector.

.6. Apparatusas definedin claim 4 andincludingmeans for adding apredetermined voltage to said bridge circuit.

7. Apparatus asdefined'in claim 4 and including means for increasing thebiasQonsaid tube.

8. :Trafl'lc control. apparatus responsive to traflic densitycomprising, apluralityo'f variable speedcontrollers operable through.repeated trafiic cycles for the control pf tratiic signals, all of saidcontrollers being connected'to a control circuit, ,meansforenergizingsaid control circuit,

each of said controllers having means foroperating the controllerthrough; saidcyclesata speed; dependent upon the voltagejon saidcontrolcircuit, a-condenser, a pluraiityof vehicleactuateddetectorsdisposedto be actuated ;by traffic niovingiiuudenthe contrclq said inals an for continuously establishing a charge of-tpredeterjrninedivalue on said condenser, said;detectors being operable uponeachwactuation thereof to vary said predetermined charge, amplifyingmeans having its input circuit corp trolledby said condenser, a powersupply-torsaidcontrel circuit including,'an, adjustable voltage control,a

' lreversiblemotorpperatively connected to said voltage .controllforadjusting the same to increase and decrease the voltage in said controlcircuit, a servo amplifier for controlling said ,motor, ,a bridgecircuit including ,the output ofsaid amplifier n eans connected to said;servo amplifier, and a feed backicircuit from said control circuit tosaid bridgecircuit.

ReEer nces-Citedin the file of this patent UNITED STATES. PATENTS2,750,576 7 Beaubien- June12,19 5 6

